Dan McGrath - XJ12 Starting Problem

About this site
The Problem
The Fix
In Use


There is a common starting problem for most Jaguar XJ series cars. Mine suffered from it, and rather than take it to the garage I decided to mend it myself.
Best of all it worked, and cost me 0p. Bargain! ;-)

....A little bit about this site

Clicking on any of the small images will open a larger version in a new browser window. (try on some of the examples above)
I hope you like the site and enjoy reading about my little project.
The site is deliberately quite simple in its design, I think this makes it clean and easy to read. I try where possible to avoid using any nasties like popups etc..
I didn't use anything other than good old notepad to design this site, dreamweaver is great - but you don't need it...

The Problem

My (otherwise lovely) 1995 X300 Jaguar XJ12 developed a very annoying starting problem.
From reading around on the internet it appears that it a general problem on all older Jaguar XJs - this problem seems to affect them all!
Some people call this the park sensor, some call it the dbc12395 switch, others call it the starter inhibitor. It's a small complicated box of switches and diodes in the bowels of the centre console!
Sometimes the car will start fine, other times it'll refuse to crank at all, and you have to wiggle the gearknob in park until the 'P' light illuminates.
Sometimes no matter how much you wiggle it (or punch it!) it just won't light up, and the car just won't start - this is particularly annoying when the sun is out as you can barely see whether the 'P' is illuminated.
Despite finding loads of other people who had this problem, or who had fixed this problem, I couldn't find any pictures of the faulty part, and how to resolve it.
That is what I'm documenting here - I hope it is of some use.


Geting the centre console out isn't so bad, I'll put more words in later, but in the meantime, here is the job in pictures.

additional switch armrest removed centre console side

dbc12395 dbc12395_2 gearbox slide switch

gearbox switch jag skislope main pcb

main pcb rear membrane buttons partially assembled centre console

radio and aircon out roller switches soldering additional switch

Switch Daughterboard

In Use

The fix has had quite a bit of time to settle in now, and so far (fingers crossed) I've had no reason to use the additional (emergency button) to start the car...
...but it's nice to know that it's there should I need it!


Well, I hope you've enjoyed what I've done, and I hope it is useful to you. It's nice to have the old girl working well again. That starting problem was so annoying.
All the best,


If you enjoyed reading about my project, and would like to leave a comment, please do!
I will post any interesting ones below.

Stop SPAM - What is 10 + 5?:

A Partridge, Le House
Lovely Stuff!
Posted: 11:17 13/05/2008

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